Reduced state incentives and new U.S. trade tariffs are likely to speed the decline of small- to medium-sized solar power installations, according to the trade group Renewable Energy Vermont.

The number of new net-metered photovoltaic panels — those that feed excess power into utilities' grids — declined by 50 percent last year, REV reported in a news release Friday, citing data from the Vermont Public Utilities Commission.

Net-metering rules that took effect January 2017 "drastically stalled the pace of customer solar projects, to levels last seen in 2014," it stated.

Community-scaled solar projects, including those for schools, towns and businesses, saw a 73 percent decline in new power generation approved for construction, the release added.

State regulators have gradually reduced incentives for net-metered projects with policies designed to more fairly share the cost of line maintenance with ratepayers who do not generate their own electricity — and to steer solar projects toward community-approved sites.

The REV statement noted that anticipated U.S. tariffs on Chinese photovoltaic panels this year will further slow Vermont's solar industry.